topic Re: Raster file missing spatial reference information in Coordinate Reference Systems Questions

Raster file missing spatial reference information

ShannonMcEwen — Fri, 08 Jan 2016 23:09:56 GMT

Hi all,

Please bear with me, I'm relearning ArcMap after using mapinfo exclusively for the last two years.

I'm trying to work with a raster data set (attached in zip file) sourced from the USGS and having issues working with it as it is missing it's spatial reference information. The raster's metadata includes the following information:

Map Projection Name: Lambert Azimuthal Equal Area
- longitude of projection center: -100.000000
- latitude of projection center: 45.000000
- false easting: 0.000000
- false northing: 0.000000
Planar Coordinate Encoding Method: row and column
- coordinate representation:
  - abscissa resolution: 1000.000000
  - ordinate resolution: 1000.000000
- planar distance units: meters
geodetic model:
- horizontal datum name: D Shpere ARC INFO
- ellipsoid name: Sphere ARC INFO
- semi major axis: 6370997.000000
- denominator of flattering ration: infinity

I've attempted to manually input the projection centers when setting the raster spacial reference but don't see any change when it runs. I've also attempted to find a complementary projection as Arc only has a polar Lambert Azimuthal Equal Area which does not work in this circumstance.

I've also tried uploading a vector layer (basic US states layer, WGS 1984) with known spatial reference before uploading the raster. That also has no effect on the raster.

Does anyone have any ideas or could help me out?

Re: Raster file missing spatial reference information

DanPatterson_Retired — Fri, 08 Jan 2016 23:18:22 GMT

open a blank dataframe

add the raster

right-click on it, select properties, and find the extent area

if the numbers are big-ish, then you have projected data

if you go to the spatial reference/coordinate system area and it says undefined, then it is undefined and needs to be

chances are, that the data are in the lambert azimuthal equal area projection... or they were lying

use the Define projection tool, and define it as such...you will have to crawl around to find it, or search by name

once it is defined, you can do anything with it, like project

Re: Raster file missing spatial reference information

MelitaKennedy — Fri, 08 Jan 2016 23:18:55 GMT

You would have to define a custom projected coordinate system in ArcGIS, but it's certainly do-able. Lambert azimuthal equal area has always supported non-polar cases in ArcGIS for Desktop, and did in Workstation too.

Anyway, here's the well-known text string for the definition:

PROJCS["raster_laz",GEOGCS["GCS_Sphere_ARC_INFO",DATUM["D_Sphere_ARC_INFO",SPHEROID["Sphere_ARC_INFO",6370997.0,0.0]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Lambert_Azimuthal_Equal_Area"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],PARAMETER["Central_Meridian",-100.0],PARAMETER["Latitude_Of_Origin",45.0],UNIT["Meter",1.0]]

Copy it as a single line to a text file, change the text file's extension to .prj, then you can import it through the raster's property page in ArcCatalog or the Define Projection tool.

Your next question may be on what geographic/datum transformation should be used to convert to NAD83 or WGS84-based coordinate system (or to overlay it with that type of data). There's no predefined transformations between a sphere-based GCS and a geodetic GCS (AKA one based on a true geodetic datum). Try just adding the raster with your other data, ignore any transformation warnings. Does it appear to overlay? Then you're good to go. If it appears to be offset north-south, try adding a custom geographic transformation (there's a tool) between its GCS and NAD83 or WGS84 whatever you're using. Set the method to Geocentric Translation and leave the parameter values set to zeroes.

Melita

Re: Raster file missing spatial reference information

DarrenWiens2 — Fri, 08 Jan 2016 23:19:04 GMT

There's no attachment.

Have you tried this as a custom CRS?

Re: Raster file missing spatial reference information

ShannonMcEwen — Tue, 12 Jan 2016 21:54:48 GMT

Thank you for the projection text string! Using your suggestion I was able to get my raster to overlay correctly on my states layer after many hours of frustration!

Re: Raster file missing spatial reference information

ShannonMcEwen — Tue, 12 Jan 2016 21:56:33 GMT

Whoops

Thanks for the image, between you and Melita, I was able to get get my raster defined and overlayed onto my states layer correctly!